Alfalfa (Medicago sativa) is perhaps the most important of forage species, providing one of the most effective sources of biological nitrogen. It is often called the “Queen of Forages” because of its highly digestible fiber and excellent protein source. Alfalfa improves soil tilth making it ideal for crop rotation.
Alfalfa breeding programs historically emphasized improving pest resistance, persistence, forage yield and forage quality. Increases in forage yield and forage quality have resulted in limited improvement. For example, see U.S. Pat. No. 4,045,912, which is incorporated herein by reference.
Breeding programs have focused on maximizing heterogeneity of the variety to improve yield and maintain stability. Heterogeneity resulted in wider variability of phenotypic features such as plant type, development rate, flowering dates, fall dormancy and winter hardiness. Hybridization of alfalfa results in greater uniformity of described traits.
A significant acreage in the Western United States has saline soils. Alfalfa is sensitive to saline soils. Salt has a deleterious effect on the growth of alfalfa seedlings. Salt also affects growth and limits yields of alfalfa. Symptoms affect stem elongation more than leaf growth. Non-dormant alfalfas have been described with salt tolerance. For example, see U.S. Pat. No. 6,005,165, which is incorporated herein by reference. However, no dormant alfalfas have been described with tolerance to salinity.